Scroll machines are becoming more and more popular for use as compressors in both refrigeration as well as air conditioning and heat pump applications due primarily to their capability for extremely efficient operation. Generally, these machines incorporate a pair of intermeshed spiral wraps, one of which is caused to orbit relative to the other so as to define one or more moving chambers which progressively decrease in size as they travel from an outer suction port towards a center discharge port. An electric motor is normally provided which operates to drive the orbiting scroll member via a suitable drive shaft.
Because scroll compressors depend upon a seal created between opposed flank surfaces of the wraps to define successive chambers for compression, suction and discharge valves are generally not required. However, when such compressors are shut down, either intentionally as a result of the demand being satisfied, or unintentionally as a result of a power interruption, there is a strong tendency for the pressurized chambers and/or backflow of compressed gas from the discharge chamber to effect a reverse orbital movement of the orbiting scroll member and the associated drive shaft. This reverse movement often generates noise or rumble which may be considered objectionable and undesirable. Further, in machines employing a single phase drive motor, it is possible for the compressor to begin running in the reverse direction should a momentary power failure be experienced. This reverse operation may result in overheating of the compressor and/or other damage to the apparatus. Additionally, in some situations, such as a blocked condenser fan, it is possible for the discharge pressure to increase sufficiently to stall the drive motor and effect a reverse rotation thereof. As the orbiting scroll orbits in the reverse direction, the discharge pressure will decrease to a point where the motor again is able to overcome this pressure head and orbit the scroll member in the forward direction. However, the discharge pressure will again increase to a point where the drive motor is stalled and the cycle is repeated. Such cycling is undesirable in that it results in excessive stresses on various components within the compressor. These components must then be increased in size or complexity in order to withstand the excessive stresses caused by this undesirable cycling.
A primary object of the present invention resides, in one embodiment, in the provision of a very simple and unique solenoid valve which can be easily assembled into a conventional gas compressor of the scroll type without significant modification of the overall compressor design, and which functions at compressor shut-down to allow gas flow from an area of intermediate pressure to an area of suction pressure. With intermediate pressure and suction pressure equalized, a leak is created from the discharge side of the compressor to the suction side of the compressor. This leak will balance the discharge gas with the suction gas thereby preventing discharge gas from driving the compressor in the reverse direction which in turn eliminates the normal shut-down noise associated with such reverse rotation.
Another object of the present invention resides, in an alternate embodiment, in the provision of a very simple and unique mechanically operated valve which can also be easily assembled into a conventional scroll compressor without significant modification of the overall compressor design, and which also functions at compressor shut-down to allow gas flow from an area of intermediate pressure to an area of suction pressure. With intermediate pressure and suction pressure equalized, a leak is created from the discharge side of the compressor to the suction side of the compressor. This leak will balance the discharge gas with the suction gas, thereby preventing reverse rotation and the attendant shut-down noise associated therewith.
Both of the primary embodiments of the present invention achieve the desired results utilizing a very simple valve which is positioned between an area of intermediate pressure and an area of suction pressure. In the first set of embodiments, the valve is actuated by a solenoid and in the second set of embodiments, the valve is actuated by a mechanical device. Additional embodiments are disclosed which also facilitate starting of the compressor which is especially applicable to compressors having low-starting-torque motors.
These and other features of the present invention will become apparent from the following description and the appended claims, taken in conjunction with the accompanying drawings.